Reset last known audio state upon losing audio focus

mLastKnownCallAudioState is checked before triggering
notification to the rest of the framework. Not resetting
this variable upon losing the audio focus results in
not sending notification to the framework later.
This commit resets mLastKnownCallAudioState during
re-initialization of the state machine.

BUG=28642858

Change-Id: I8740c4c55a523cedf1e9aba1bf1c55fdda94dd1b
diff --git a/src/com/android/server/telecom/CallAudioRouteStateMachine.java b/src/com/android/server/telecom/CallAudioRouteStateMachine.java
index 5234a82..d7c6dfa 100644
--- a/src/com/android/server/telecom/CallAudioRouteStateMachine.java
+++ b/src/com/android/server/telecom/CallAudioRouteStateMachine.java
@@ -1291,6 +1291,7 @@
         setMuteOn(mIsMuted);
         mWasOnSpeaker = false;
         mHasUserExplicitlyLeftBluetooth = false;
+        mLastKnownCallAudioState = initState;
         transitionTo(mRouteCodeToQuiescentState.get(initState.getRoute()));
     }
-}
\ No newline at end of file
+}